If an injection nozzle is not properly delivering fuel into the pre-combustion chamber of a cylinder, driveability could be greatly affected, or a DTC may set. If other diagnosis indicates, or if the injection nozzles are suspected of not properly delivering fuel, they should be tested. Typically, a nozzle failure can be detected by using the injector balance test.

Nozzle testing is comprised of the following checks:

An injector balance test is performed with the scan tool. This test will properly identify a stuck closed or a noisy injector nozzle, the most common types of nozzle failure.

1. Install the scan tool.
2. Start the engine.
3. Allow the engine to idle.
4. Perform the injector balance test on each cylinder. A balance test refers to a specific cylinder.

If a suspect nozzle is located, switch the nozzle to the adjacent cylinder, and repeat the balance test to positively identify the malfunctioning nozzle.

5. Locate and replace the malfunctioning nozzle and the glow plug.

Caution: Do not place your hands or arms near the tip of the nozzle when testing the nozzles. The high pressure atomized fuel spray from a nozzle has sufficient penetrating power to puncture flesh and destroy tissue. This may result in blood poisoning. Always enclose the nozzle tip in a receptacle, preferably transparent, in order to contain the spray.

Important: The Injector Nozzle Opening Pressure and Leakage tests should be performed only on vehicles with high mileage, engines that have been over heated, or vehicles that pull heavy loads. False or inaccurate readings can occur if the following tests are not performed to the above criteria.

Important: Each test should be considered independent of the others. For example, when checking the opening pressure, do not check for leakage. If all of the following tests are satisfied, the nozzle assembly can be reused. If any one of the tests is not satisfied, the complete nozzle assembly must be replaced. When performing the injection nozzle tests, refer to the instructions provided with the J 29075-B Nozzle Tester.

1. Open the shut-off valve at the pressure gauge one-quarter turn.
2. Depress the tester lever slowly. Note at what pressure the needle of the pressure gauge stopped. The maximum observed pressure is the opening pressure. Some nozzles may pop while other nozzles may drip down (this is not leakage).
3. The opening pressure should not fall below the lower limit of 105 bar (1500 psi) for naturally aspirated engines and 117 bar (1700 psi) for turbo-charged engines for used nozzles.
4. Replace the nozzles that fall below the lower limit.

Caution: When testing nozzles, do not place your hands or arms near the tip of the nozzle. The high pressure atomized fuel spray from a nozzle has sufficient penetrating power to puncture flesh and destroy tissue and may result in blood poisoning. The nozzle tip should always be enclosed in a receptacle, preferably transparent, to contain the spray.

Important: The Injector Nozzle Opening Pressure and Leakage tests should be performed only on nozzles with high mileage, engines that have been over heated, or on vehicles that pull heavy loads. False or inaccurate readings can occur if the following tests are not performed to the above criteria.

1. Open the shut-off valve at the pressure gauge (one turn).
2. Blow dry the nozzle tip.
3. Slowly depress the lever of the manual test stand until the gauge reads a pressure of 95 bar (1400 psi).
4. Observe the nozzle tip. A drop may form on the end of the nozzle but should not drop off within a period of 10 seconds.
5. Replace the nozzle assembly if a drop falls during the 10 seconds.